This invention has to do with rock bits of the type used for drilling into the earth, and more particularly, is concerned with improvements in the roller cutter components of well drilling bits.
Rock bits of the rotary type generally comprise a body having one or more downwardly extending legs, each of which is provided with a downwardly and inwardly extending journal on which a roller cutter is mounted for rotation under the force of engagement of the weighted bit body and the face of the formation being drilled. For purposes of fracturing and gouging the formation face, the roller cutters, which may be cylindrical in configuration, are provided with a peripherally distributed series of relatively harder tooth-like cutting elements, usually referred to as hard metal inserts. The hard metal inserts may be fabricated of tungsten carbide or similar hard wearing material.
In well drilling the bit body is rotated about the well axis and the body carried roller cutters rotate on their own axis disposed angularly relative to the well axis. As the roller cutters rotate successive ones of the mentioned hard metal inserts bear against the formation and penetrate and fracture the formation face for removal by drilling mud as drilling proceeds. Drilling continues in this manner until the bit, i.e. its roller cutters, are too warn to continue effectively. At this point the drill string must be pulled and a new bit attached and the string relowered to the hole bottom. The downtime required for changing the bit and the labor involved are such that fewer needed bit changes are highly desired.